This invention relates to a heat exchange apparatus, and more particularly, to a heat exchange apparatus which facilitates the uniform transfer of heat.
Many heat exchange devices have been developed over the years. These devices have as their purpose the tranfer of heat from one substance to another. These various configurations and designs have envisioned myriads of small tubes, conduits, plates and other configurations all directed toward achieving a maximum amount of transfer of heat between the substances in question. In some instances this substance may be fluids; in other cases they may be gases or solids.
In recent years much work has been directed toward making greater usage of the radiant heat energy of the sun. One method of effecting such usage of the sun's energy for heating purposes is to utilize a thermal energy storage material which is capable of storing heat energy. A material is selected that has a freezing point or a boiling point at or around the temperatures which may be generated by the sun's heat energy. The sun's heat energy is then stored by converting the state of the substance from a solid to a liquid or to a liquid from a gas using, respectively, the heat of fusion or the heat of vaporization of the substance.
In this manner, relatively small weights of materials may be used to store large amounts of heat. For example, when using thermal energy storage materials on sunny winter days, air that has been heated by solar collectors on the roof, say, of a house may be fed past the basement containers of a heat exchange unit filled with the thermal energy storage material (hereinafter referred to as TES). The TES then melts in the process and thereby stores heat for evening use. In the summer the system may be used in the reverse. The cool incoming night air freezes the TES such that it may cool the warm air coming in during the day as it melts. The melting of the TES material in effect is a cooling process which absorbs heat from the surrounding air. Conversely, the freezing process of the TES material gives up heat to the air and thus may be referred to as a heating process.
Whatever the TES material used, it is necessary, particularly for home heating and cooling, that the heating and cooling processes utilizing the TES material be such that heat is withdrawn from or stored in the TES material uniformly, i.e., at a known constant rate. Many of the present day heat exchange units do not achieve such uniform heat transfer. On the contrary, many heat exchange units tend to transfer heat energy more slowly as the TES material melts and decreases in surface area and mass.
It is, therefore, an object of this invention to provide an improved heat exchange apparatus which is capable of a more uniform exchange of heat between a thermal storage material and a surrounding fluid.
Another object of this invention is to provide an improved heat exchange apparatus which effects a more uniform melting or freezing of the thermal storage material.